U.S. patent number 9,246,229 [Application Number 13/990,375] was granted by the patent office on 2016-01-26 for antenna arrangement with an elongated structure for guiding an electromagnetic wave.
This patent grant is currently assigned to TELEFONAKTIEBOLAGET L M ERICSSON (PUBL). The grantee listed for this patent is Henrik Asplund, Anders Derneryd, Jonas Medbo. Invention is credited to Henrik Asplund, Anders Derneryd, Jonas Medbo.
United States Patent |
9,246,229 |
Asplund , et al. |
January 26, 2016 |
**Please see images for:
( Certificate of Correction ) ** |
Antenna arrangement with an elongated structure for guiding an
electromagnetic wave
Abstract
An antenna arrangement comprising at least a first and a second
elongated structure, e.g., a coaxial cable, for guiding an
electromagnetic wave is provided. Each of said structures comprises
a plurality of radiation elements. The structures are positioned
alongside each other in their longitudinal direction of extension
forming a bundle. The elongated structures are arranged within the
bundle such that the radial positions of said structures are
alternated in the longitudinal direction of extension.
Inventors: |
Asplund; Henrik (Stockholm,
SE), Derneryd; Anders (Goteborg, SE),
Medbo; Jonas (Uppsala, SE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Asplund; Henrik
Derneryd; Anders
Medbo; Jonas |
Stockholm
Goteborg
Uppsala |
N/A
N/A
N/A |
SE
SE
SE |
|
|
Assignee: |
TELEFONAKTIEBOLAGET L M ERICSSON
(PUBL) (Stockholm, SE)
|
Family
ID: |
44475141 |
Appl.
No.: |
13/990,375 |
Filed: |
November 29, 2010 |
PCT
Filed: |
November 29, 2010 |
PCT No.: |
PCT/EP2010/068445 |
371(c)(1),(2),(4) Date: |
May 29, 2013 |
PCT
Pub. No.: |
WO2012/072102 |
PCT
Pub. Date: |
June 07, 2012 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20130257669 A1 |
Oct 3, 2013 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01Q
21/205 (20130101); H01Q 13/22 (20130101); H01Q
21/28 (20130101); H01Q 13/203 (20130101); H01Q
1/007 (20130101); H01Q 1/521 (20130101) |
Current International
Class: |
H01Q
13/10 (20060101); H01Q 21/20 (20060101); H01Q
21/28 (20060101); H01Q 13/22 (20060101); H01Q
1/00 (20060101); H01Q 1/52 (20060101); H01Q
13/20 (20060101) |
Field of
Search: |
;343/770,771,767 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
101404350 |
|
Apr 2009 |
|
CN |
|
63290416 |
|
Nov 1988 |
|
JP |
|
2005 190896 |
|
Jul 2005 |
|
JP |
|
2005 286812 |
|
Oct 2005 |
|
JP |
|
Other References
Office Action dated Jul. 2, 2014, issued in Chinese Patent
Application No. 201080070405.2, 7 pages. cited by applicant .
Tago et al. "Design and Characteristics of Radiating Pair Cable"
Proceedings of International Wire and Cable Symposium, Nov. 1,
1983, vol. 32, pp. 30-36. cited by applicant.
|
Primary Examiner: Le; Hoanganh
Attorney, Agent or Firm: Rothwell, Figg, Ernst &
Manbeck, P.C.
Claims
The invention claimed is:
1. An antenna arrangement comprising: at least a first and a second
elongated structure for guiding an electromagnetic wave, each of
said structures including a plurality of radiation elements,
wherein said plurality of radiation elements are through-going
perforations in said elongated structures, each of said structures
exhibiting a longitudinal direction of extension, wherein said
structures are positioned alongside each other in their
longitudinal direction of extension forming a bundle, and wherein
said structures are arranged within the bundle such that the radial
positions of said structures are alternated in the longitudinal
direction of extension.
2. The antenna arrangement according to claim 1, wherein said
structures form a flat bundle.
3. The antenna arrangement according to claim 2, wherein said
structures are plaited, braided, pleated or wounded.
4. The antenna arrangement according to claim 2, wherein at least
one of said structures is folded at a first side of the bundle to a
second side of the bundle.
5. The antenna arrangement according to claim 1, wherein said
structures form a circular bundle.
6. The antenna arrangement according to claim 5, wherein said
structures are twisted.
7. The antenna arrangement according to claim 5, wherein the bundle
includes a core and said structures are twisted around said
core.
8. The antenna arrangement according to claim 1, wherein said
structures are a coaxial cable.
9. The antenna arrangement according to claim 1, further
comprising: a locking arrangement for locking the structures in a
predetermined position relative to each other with respect to their
longitudinal extensions and relative to a distance between the
structures.
10. The antenna arrangement according to claim 9, wherein the
locking arrangement includes a sheathing of a non-conducting
material at least partly surrounding each of said structures.
11. The antenna arrangement according to claim 9, wherein the
locking arrangement includes a filling of a non-conducting material
at least partly surrounding each of said structures.
12. The antenna arrangement according to claim 9, wherein the
locking arrangement includes one or more of the following: an
interacting protrusions in one of the structures and interacting
apertures in the other structure, locking bands and hook and loop
type fasteners.
13. The antenna arrangement according to claim 9, wherein the
locking arrangement includes interacting protrusions in the first
elongated structure and corresponding interacting apertures in the
second elongated structure.
14. The antenna arrangement according to claim 1, wherein each of
the radiation elements extend in a direction perpendicular to the
longitudinal direction.
Description
CROSS REFERENCE TO RELATED APPLICATION(S)
This application is a 35 U.S.C. .sctn.371 National Phase Entry
Application from PCT/EP2010/068445, filed Nov. 29, 2010,
designating the United States, the disclosure of which is
incorporated herein in its entirety by reference.
TECHNICAL FIELD
The present invention discloses a novel antenna arrangement.
BACKGROUND
When deploying wireless communications systems such as, for
example, cellular systems, in indoor environments in general,
traditional kinds of antennas can be less suitable to use. In such
environments, use is sometimes instead made of so called "leaky
cables", also sometimes referred to as leaky feeders or radiating
cables.
A leaky cable is a cable which is capable of conducting
electromagnetic radio frequency energy, and which has been provided
with apertures in order to make the cable radiate, i.e. to allow
some of the energy to "leak" from the cable, thus enabling the
cable act as an antenna. Such an antenna, i.e. a leaky cable, will
due to reciprocity be able to act equally well as a receiving as a
transmitting antenna. Due to its nature of a cable, a "leaky cable
antenna" will, as compared to a traditional antenna, act more like
a line source than a point source, thus making it easier to obtain
coverage in tunnels, along railways or where a high degree of
"shadowing" occurs when using a point source antenna. An example of
the latter is an indoor scenario, e.g. an office landscape.
In recent years demands for high user bitrates and capacity have
increased dramatically due to the growth of mobile broadband usage.
In order to achieve higher user bitrates and spectrum efficiency
multiple antenna techniques like Multiple Input Multiple Output
(MIMO) are employed in wireless communications systems.
In deployments where multiple leaky feeders are used it is a great
benefit, regarding installation, to bundle them. However, the
individual characteristics of the cables may differ substantially
regarding directivity. If more than two cables are bundled there
might also be significant radiation efficiency differences due to
mutual coupling. Azimuth antenna patterns for two cables which are
bundled and extended along an axis perpendicular to the figure are
shown in FIG. 1. As can be seen in the figure, a problem is that
the antenna patterns only partly cover the same angular interval. A
consequence is power imbalance for the different antenna branches
of the leaky cables which is particularly prominent in
line-of-sight conditions. The power imbalance is a problem in e.g.
MIMO multi stream transmissions causing reduced capacity.
SUMMARY
It is therefore an object of the present invention to address some
of the problems and disadvantages outlined above and to provide an
antenna arrangement with leaky cables which has improved properties
as compared to the prior art.
The above stated object is achieved by means of an antenna
arrangement according to the independent claims, and by the
embodiments according to the dependent claims.
According to an embodiment of the present invention an antenna
arrangement comprising at least a first and a second elongated
structure for guiding an electromagnetic wave is provided. Each one
of the structures comprises a plurality of radiation elements and
each structure exhibits a longitudinal direction of extension.
Moreover, the structures are positioned alongside each other in
their longitudinal direction of extension forming a bundle.
Additionally, the structures are arranged within the bundle such
that the radial positions of said structures are alternated in the
longitudinal direction of extension.
An advantage of embodiments of the present invention is that they
provide an antenna arrangement suitable for MIMO multi stream
transmissions.
Yet another advantage of embodiments is that they even out the
radiation performance and improve the link gains along the
extension of elongated structures comprising the plurality of
radiation elements.
Further advantages and features of embodiments of the present
invention will become apparent when reading the following detailed
description in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding, reference is made to the following
drawings and preferred embodiments of the invention.
FIG. 1 shows typical azimuth antenna patterns for a prior art
antenna solution including two leaky cables.
FIG. 2a depicts a first example of an embodiment of a twisted pair
bundle of leaky feeders and FIG. 2b is a sectional view of the same
example.
FIG. 2c shows azimuth antenna patterns for the first example of an
embodiment.
FIG. 3a depicts a second example of an embodiment of a flat bundle
of four leaky feeders and FIG. 3b is a sectional view of the same
example.
FIG. 3c shows azimuth antenna patterns for the second example of an
embodiment.
FIG. 4a depicts a third example of an embodiment of a hawser like
bundle of multiple leaky feeders and FIG. 4b is a sectional view of
the same example.
FIG. 5 shows a sectional view of a fourth example embodiment of the
invention comprising a locking arrangement.
FIG. 6 shows a sectional view of fifth example of an embodiment of
the invention.
DETAILED DESCRIPTION
The invention will be described below with reference to the
accompanying drawings, in which the structures for guiding an
electromagnetic wave are shown as coaxial cables. It should however
be pointed out that this is merely an example intended to enhance
the reader's understanding of the invention and should not be seen
as limiting the choice of structure, which can, for example, also
comprise one or more of the following: waveguides, strip line
arrangements, micro strip arrangements.
In addition, the invention will be described by means of examples
which comprise two or more structures or cables. Again, the number
of cables shown is merely an example intended to enhance the
reader's understanding of the invention, and should not be seen as
limiting the number of cables which can be used within the scope of
the present invention. In the drawings, like reference signs refer
to like elements.
A concept of the embodiments described hereinafter is to provide an
antenna arrangement comprising at least two elongated structures,
e.g. coaxial cables, for guiding an electromagnetic wave, and
wherein each of said structures comprising a plurality of radiation
elements. The elongated structures exhibit a longitudinal direction
of extension and are positioned alongside each other in their
longitudinal direction of extension forming a bundle. Furthermore,
the structures are arranged within the bundle such that the radial
positions of said structures are alternated in the longitudinal
direction of extension. Thus, by cyclically change position of the
location of each structure in the cross-section of the bundle, the
occurrence is equal for all structures at all positions along the
extension of the bundle. In this way the average radiation pattern
is equal for all structures.
Moreover, when the structures within the bundle are regularly
interchanged such that all structures occupy each specific location
in the cross-section of the bundle with the same frequency i.e.
probability, the link gains of the different structures are evened
out. Moreover, any radiation efficiency imbalance is also evened
out. The antenna arrangement will also enable improved MIMO channel
performance especially in line of sight conditions.
There are multiple ways of achieving equal probability of the
structure locations in a cross-section of the bundle, along the
extension of the bundle, whereof some are described in detail in
the following.
In the following the above mentioned embodiments will be further
explained with reference to FIGS. 2a-2c, 3a-3c, 4a-4b, 5 and 6.
In FIG. 2a a first example of an embodiment 100 of the invention is
shown and in FIG. 2b a sectional view of the same example is
depicted. The embodiment 100 comprises a first 110 elongated
structure and a second 120 elongated structure, e.g. coaxial
cables, each of which comprises an inner conductor 112, 122 and an
outer conductor 114, 124, which are separated from the respective
inner conductor by a dielectric layer 116, 126. An alternative to a
dielectric layer is a dielectric spacer, i.e. a spacer of a
dielectric material. Both coaxial cables 110, 120 exhibit a
longitudinal direction of extension and are positioned alongside
each other in their longitudinal direction of extension forming a
bundle. The first cable 110 comprises a plurality of radiation
elements 118 and the second cable 120 also comprises a plurality of
radiation elements 128. Not all of the radiation elements are shown
in FIG. 2a nor have all of the shown radiation elements been
provided with reference numbers.
The radiation elements of the embodiment 100 are elongated slots
which are through-going perforations in the outer conductor 114,
124, and have a main direction of extension which makes the slots
radiate. The main direction of extension which makes a slot radiate
differs between different kinds of cables: in a coaxial cable, as
shown in the drawings, the main direction of extension should not
coincide with the cable's main length of extension. In a waveguide,
or a micro strip or strip line structure, the main direction of
extension of a slot can coincide with that of the structure or
cable and still radiate. Regarding the exact shape of the radiation
elements, it should be pointed out that although they are shown as
elongated slots in the drawings and referred to in this way in the
description, the shape of the radiation elements can be chosen from
a wide variety of different kinds of perforations in the outer
conductor, although preferred embodiments include elongated
rectangular or oval slots. It should however be pointed out that
most shapes of perforations will give rise to a radiating effect.
Also, with reference to other kinds of possible structures for
guiding an electromagnetic wave, such as waveguides or strip line
and micro strip structures, it can be pointed out that the
perforations which form the radiation elements should be made in
the conductor of such structures. However, all elongated structures
forming the bundle should preferably comprise perforations of
approximately the same shape and distribution.
Furthermore, as shown in FIG. 2a the cables 110, 120 are twisted
i.e. they are arranged within the bundle such that the radial
positions of the cables are alternated in the longitudinal
direction of extension. Thus, by cyclically changing position of
the location of each cable 110, 120 in the cross-section of the
bundle, the occurrence is equal for both cables 110, 120 at all
positions along the extension of the bundle. The described example
of embodiment 100 of the invention will typically cause both cables
to radiate with similar characteristics. Azimuth antenna patterns
for the embodiment 100 are shown in FIG. 2c. The antenna pattern of
the first cable 111 and the antenna pattern of the second cable 121
cover the same angular interval, which can be seen in the figure.
Thus, the power is balanced for the different antenna branches of
the cables, which is particularly advantageous in line-of-sight
conditions.
In addition, the embodiment 100 may be used as an antenna for MIMO
applications, Multiple Output Multiple Input. In MIMO applications,
two different data streams D.sub.1 and D.sub.2 may be transmitted,
one in each cable 110, 120, or both streams may be transmitted in
both cables 110, 120, if the appropriate gain and/or phase
weighting of the data streams is applied. The embodiment 100 is
highly suitable for MIMO applications, since the two cables will
have very similar radiation patterns, thereby reducing the
likelihood of power imbalance in the MIMO channel which would
otherwise result in reduced capacity.
In FIG. 3a a second example of an embodiment 200 of the invention
is shown and in FIG. 3b a sectional view of the same example is
depicted. The embodiment 200 comprises a first 210 elongated
structure, a second 220 elongated structure, a third elongated
structure 230 and a fourth elongated structure 240 e.g. coaxial
cables, each of which comprises an inner conductor 212, 222, 232,
242 and an outer conductor 214, 224, 234, 244 which are separated
from the respective inner conductor by a dielectric layer 216, 226,
236, 246. An alternative to a dielectric layer is a dielectric
spacer, i.e. a spacer of a dielectric material. All coaxial cables
210, 220, 230, 240 exhibit a longitudinal direction of extension
and are positioned alongside each other in their longitudinal
direction of extension forming a substantially flat bundle. Each
cable 210, 220, 230, 240 comprises a plurality of radiation
elements 218, 228, 238, 248, respectively. For reasons of clarity,
not all of the radiation elements are shown in FIG. 3a nor have all
of the shown radiation elements been provided with reference
numbers.
The radiation elements of the embodiment 200 are also elongated
slots which are through-going perforations in the outer conductor
214, 224, 234, 244, and have a main direction of extension which
makes the slots radiate. Preferably, the shape and the distribution
of the perforations are approximately equal for all cables.
Furthermore, as shown in FIG. 3a the cables 210, 220, 230, 240 are
arranged within the bundle such that the radial positions of the
cables 210, 220, 230, 240 are alternated in the longitudinal
direction of extension. The alternation of radial positions of the
cables 210, 220, 230, 240 may be formed by folding at least one
cable residing at a first side of the bundle to a second side of
the bundle. Thus, by cyclically changing position of the location
of each cable 210, 220, 230, 240 in the cross-section of the
bundle, the occurrence is equal for all cables 210, 220, 230, 240
at all positions along the extension of the bundle. Furthermore,
the alternation of radial positions of the cables 210, 220, 230,
240 may be formed by different kinds of folding techniques such as
plaiting, braiding, pleating or wounding.
The described example of embodiment 200 of the invention will
typically cause all cables to radiate with similar characteristics.
Azimuth antenna patterns for the embodiment 200 are shown in FIG.
3c. The antenna pattern of the first cable 211, the antenna pattern
of the second cable 221, the antenna pattern of the third cable 231
and the antenna pattern of the fourth cable 241 cover the same
angular interval, which can be seen in the figure. Thus, the power
is balanced for the different antenna branches of the cables, which
is particularly advantageous in line-of-sight conditions.
In addition, the embodiment 200 can also be used as an antenna for
MIMO applications, Multiple Output Multiple Input. In MIMO
applications, up to four different data streams D.sub.1, D.sub.2,
D.sub.3 and D.sub.4 may be transmitted, one in each cable 210, 220,
230, 240, or up to four streams may be transmitted in all cables
210, 220, 230, 240, if the appropriate gain and/or phase weighting
of the data streams is applied. The embodiment 200 is highly
suitable for MIMO applications, since the four cables radiate
mainly within the same angular interval reducing the likelihood of
power imbalance in the MIMO channel. Thus, the capacity of the
antenna arrangement is improved.
An advantage with the embodiment 200 of the present invention shown
in FIGS. 3a and 3b is that it enables installation where limited
thickness of the antenna arrangement is allowed, such as when
installing on a flat surface such as a wall or ceiling. Another
advantage of the embodiment 200 of the present invention is that it
provides the possibility to arrange the antenna arrangement to
radiate mainly in one direction i.e. by placing the radiation
elements of each outer conductor 214, 224, 234, 244 on the same
side of the bundle.
In FIG. 4a a third example of an embodiment 300 of the present
invention is shown and in FIG. 4b a sectional view of the same
example is depicted. The embodiment 300 comprises a plurality of
elongated structure 310-370, e.g. coaxial cables, each of which
comprises an inner conductor 312-372 and an outer conductor 314-374
which are separated from the respective inner conductor by a
dielectric layer 316-376. An alternative to a dielectric layer is a
dielectric spacer, i.e. a spacer of a dielectric material. All
coaxial cables 310-370 exhibits a longitudinal direction of
extension and are positioned alongside each other in their
longitudinal direction of extension forming a substantially
circular bundle. Each cable 310-370 comprises a plurality of
radiation elements, respectively. For reasons of clarity, only some
of the radiation elements 318-358 of some of the cables are shown
in FIG. 4a. It should also be pointed out that not all of the shown
radiation elements have been provided with reference numbers.
The radiation elements of the embodiment 300 are also in this
embodiment elongated slots which are through-going perforations in
the outer conductor 310-370, and have a main direction of extension
which makes the slots radiate. Preferably, the shape and the
distribution of the perforations are approximately equal for all
cables.
Furthermore, as shown in FIG. 4a the cables 310-370 are arranged
within the bundle such that the radial positions of the cables
310-370 are alternated in the longitudinal direction of extension.
The alternation of radial positions of the cables 310-370 may be
formed by twisting the cables around a core 302. Thus, by
cyclically changing position of the location of each cable 310-370
in the cross-section of the bundle, the occurrence is equal for all
cables 310-370 at all positions along the extension of the bundle.
The core 302 may comprise a conducting material to avoid absorption
loss if any slots radiate in a direction towards the core. However,
in another embodiment the core 302 may comprise a non-conducting
material. An advantage of the described example of the embodiment
300 of the invention is that when the core comprises a conducting
material, absorption loss could be avoided when radiation elements
318-378 radiate inwards.
Also the embodiment 300 shown in FIGS. 4a and 4b can be used as an
antenna for MIMO applications. In MIMO applications, up to seven
different data streams D.sub.1-D.sub.7 may be transmitted, one in
each cable 310-370, or up to seven streams may be transmitted in
all cables 310-370, if the appropriate gain and/or phase weighting
of the data streams is applied. The embodiment 300 is highly
suitable for MIMO applications, since the seven cables radiate
mainly within the same angular interval.
FIG. 5 shows a sectional view of a fourth embodiment 400 of an
antenna arrangement which can be applied to any of the embodiments
shown in FIGS. 2-4, but which is here shown applied to the
embodiment 300 of FIG. 4. In order to ensure the proper distances
and angles between the cables 310-370 in the antenna arrangement
300, the cables 310-370 are locked in their positions with respect
to each other by a locking arrangement 410. That is, the locking
arrangement locks the cables in a predetermined position relative
to each other with respect to their longitudinal extensions and to
a distance between the cables. The locking arrangement 410 can be
designed in a number of ways, such as, for example interacting
protrusions in one of the cables and interacting apertures in the
other cable, locking bands or hook and loop type fasteners. In some
embodiments these locking arrangements assume that each cable is
surrounded by a protective non-conducting sheathing, such as rubber
sheathing.
The locking arrangement 410 in the arrangement of FIG. 5 is however
different from the ones listed above: instead, the cables 310-370
shown in FIG. 5 are partly encased in a piece of dielectric
material 410, e.g. plastic, which locks them in place, i.e. there
is a sheathing of a non-conducting material at least partly
surrounding each of the cables. In another embodiment the locking
arrangement may comprise a filling of a non-conducting material at
least partly surrounding each of the cables
FIG. 6 shows a sectional view of a fifth example of an embodiment
500. In this embodiment the alternation of radial positions of the
cables 510-540 may be formed by twisting the cables around a core
502 in a way described in conjunction with embodiment 300 shown in
FIG. 4. However, in the embodiment 500 the cross-section of the
cables may be formed to be a part of the locking arrangement,
insuring the proper distances and angles between the cables as
shown in FIG. 6.
Also, it should be pointed out that although the arrangement of the
invention has been described above primarily with reference to
transmission, the inventive arrangement works equally well for
reception, and will thus be able to be used for receive diversity
or MIMO reception.
The present invention is not limited to the above-described
preferred embodiments. Various alternatives, modifications and
equivalents may be used. Therefore, the above embodiments should
not be taken as limiting the scope of the invention, which is
defined by the appending claims.
* * * * *